SEARCH · USGS Science

Results for “CHANCE”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 343 records · Page 19Linked to original sources

USGS2017

Status and threats analysis for the Florida manatee ( Trichechus manatus latirostris ), 2016

Trichechus manatus (West Indian manatee), especially T. m. latirostris , the Florida subspecies, has been the focus of conservation efforts and extensive research since its listing under the Endangered Species Act of 1973. To determine the status of, and severity of threats to, the Florida manatee, a comprehensive revision and update of the manatee Core Biological Model was completed and used to perform a population viability analysis for the Florida manatee. The probability of the Florida manatee population falling below 500 adults on either the Gulf or East coast within the next 100 years was estimated to be 0.42 percent. This risk of quasi-extinction is low because the estimated adult survival rates are high, the current population size is greater than 2,500 on each coast, and the estimated carrying capacity for manatees is much larger than the current abundance estimates in all four regions of Florida. Three threats contribute in roughly equal measures to the risk of quasi-extinction: watercraft-related mortality, red-tide mortality, and loss of warm-water habitat. Only an increase in watercraft-related mortality has the potential to substantially increase the risk of quasi-extinction at the statewide or coastal level. Expected losses of warm-water habitat are likely to cause a major change in the distribution of the population from the regions where manatees rely heavily on power plant effluents for warmth in winter (Southwest and Atlantic regions) to the regions where manatees primarily use natural springs in winter (Northwest and Upper St. Johns regions). The chances are nearly 50 percent that manatee populations in the Southwest and Atlantic regions will decrease from their 2011 levels by at least 30 percent over the next century. A large number of scenarios were examined to explore the possible effects of potential emerging threats, and in most of them, the risk of quasi-extinction at the coastal scale within 100 years did not rise above 1 percent. The four exceptions are scenarios in which the rate of watercraft-related mortality increases, carrying capacity is only a fraction of the current estimates, a new chronic source of mortality emerges, or multiple threats emerge in concert. Even in these scenarios, however, the risk of falling below 500 adults on either the East coast or the Gulf coast within 100 years from 2011 is less than 10 percent. High adult survival provides the population with strong resilience to a variety of current and future threats. On the basis of these analyses, we conclude that if these threats continue to be managed effectively, manatees are likely to persist on both coasts of Florida and remain an integral part of the coastal Florida ecosystem through the 21st century. If vigilance in management is reduced, however, the scenarios in which manatees could face risk of decline become more likely.

Florida↗

USGS2019

Quantifying the eroded and deposited mass of mercury-contaminated sediment by using terrestrial laser scanning at the confluence of Humbug Creek and the South Yuba River, Nevada County, California, 2011–13

High-resolution, terrestrial laser scanning, also known as ground-based lidar (light detection and ranging), was used to quantify the volume of mercury-contaminated sediment eroded from an outcrop of historical placer-mining debris at the confluence of Humbug Creek and the South Yuba River in the Sierra Nevada foothills, about 17 kilometers northeast of Grass Valley, California, and delivered to a zone below an observed flood stage of the South Yuba River. Substantial quantities of mercury were used and lost to the environment from historical placer gold mining activities on the western slope of the Sierra Nevada, California, and recent studies have documented continued persistence of mercury and methylmercury concentrations in water, sediment, fish, and predatory invertebrates in the Yuba River drainage basin in relation to suspected mercury sources. To identify areas that have high levels of mercury contamination as possible remediation targets in the Yuba River drainage basin and other areas in the Sierra Nevada, the U.S. Geological Survey worked in cooperation with the Bureau of Land Management on this and other detailed studies. Malakoff Diggings, one of the largest hydraulic gold mines in the Sierra Nevada, is 3.5 kilometers north of the study site in the Humbug Creek subbasin. Terrestrial laser scanning was used to produce centimeter-scale, three-dimensional maps of the complex outcrop surface, which was composed of an upper erosional area (cliff and over-steepened slope) and a lower depositional area (colluvial slope). The outcrop could not be mapped non-destructively or in sufficient detail by traditional surveying techniques. The study site, which was approximately 70 meters long, 30 meters wide and 20 meters high, was surveyed four times in 2 years (December 15, 2011; October 25, 2012; January 4, 2013; and November 22, 2013) to determine volumetric differences in the upper erosional and lower depositional areas between surveys. Measured changes in volume for the upper erosional area and lower depositional area were multiplied by the corresponding sediment density so that a mass-balance relationship, between the eroded and deposited sediment during each period, could be used to estimate the amount of mercury-contaminated sediment that was transported to below the base of the colluvial slope, where it could be mobilized by the South Yuba River during a flood having a 5-to-10-year recurrence interval. On December 2, 2012, a flood of this estimated magnitude reached the base of the colluvial slope. Between the first and second surveys (December 15, 2011–October 25, 2012), an estimated mass of 18±9.2 kilograms of sediment was transported from steeper slopes to the gently sloping river bank below the base of the colluvial slope. Between the second and third surveys (October 25, 2012–January 4, 2013), an atmospheric river caused heavy precipitation at the study site during late November and early December 2012. This short-duration, high-intensity rain resulted in a large amount of erosion and deposition at the study site and also caused high streamflow (flood stage) in the South Yuba River. From October 2012 to January 2013, 51±31 kilograms of sediment was transported to below the base of the colluvial slope, that is, below the high-water mark of December 2, 2012. Between the third and fourth surveys (January 4, 2013–November 22, 2013), an additional 10±26 kilograms of sediment was transported to below the base of the colluvial slope. During the 24 months of the study, the total mass of sediment delivered below the base of the colluvial slope and the high-water mark of December 2, 2012, was 79±66 kilograms. In any given year there is a 10–20-percent chance (5-to-10-year recurrence interval) of a flood equal to or greater than that of the December 2, 2012, flood, which could transport mercury-contaminated sediment at the study site into the South Yuba River. Hydraulically modeled estimates of the South Yuba River stage during floods having a 50- and 100-year recurrence interval (2- and 1-percent annual exceedance probability, respectively) indicated that resulting river stages could be 2.2–3.0 meters above the base of the colluvial slope, or 2.2–3.0 meters above the high-water mark of December 2, 2012. Such high river stages would be likely to inundate the lower half of the colluvial slope and mobilize a substantial volume of mercury-contaminated sediment to downstream areas.

California↗

USGS2021

Development of regression equations for the estimation of the magnitude and frequency of floods at rural, unregulated gaged and ungaged streams in Puerto Rico through water year 2017

The methods of computation and estimates of the magnitude of flood flows were updated for the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent chance exceedance levels for 91 streamgages on the main island of Puerto Rico by using annual peak-flow data through 2017. Since the previous flood frequency study in 1994, the U.S. Geological Survey has collected additional peak flows at additional streamgages, and Puerto Rico has experienced numerous flood events. This updated study was performed using longer annual peak-flow datasets from more stations to provide more representative equations to predict flood flows. Screening criteria for these streamgages included 10 or more years of annual peak-flow data, unregulated flow, and less than 10 percent impervious drainage area. The magnitude and frequency of floods at selected streamgages in Puerto Rico were estimated using updated methods outlined in Bulletin 17C. The new procedures include a regional skew analysis that incorporates Bayesian regression techniques, the Expected Moments Algorithm to better represent missing record and estimate parameters of the log-Pearson Type III distribution, and the Multiple Grubbs-Beck test for low outlier detection. Regional regression equations were developed to estimate peak-flow statistics at ungaged locations by using selected basin and climatic characteristics as explanatory variables. These variables were determined from digital spatial datasets and geographic information systems by using the most recent data available. Ordinary least-squares regression techniques were used to filter the basin characteristics and determine two separate regions, region 1 (west) and region 2 (east), based on residuals. A generalized least-squares procedure was used to account for cross-correlation of sites and develop the final set of equations that have drainage area as the only explanatory variable. The average standard errors of prediction ranged from 18.7 to 46.7 percent in region 1 and 33.4 to 57.6 percent in region 2 for all annual exceedance probabilities (AEPs) examined. The updated statistics showed a greater accuracy of prediction when compared to those from the previous study using drainage area as the only explanatory variable for all AEPs examined in region 1 and the 0.01 and 0.002 AEP flows for region 2. When compared to equations developed in the previous study that have drainage area, mean annual rainfall, and (or) depth-to-rock as explanatory variables, the updated statistics show a greater accuracy of prediction in region 1 at AEP flows of 0.02 and lower (that is, higher flows). Those developed for region 2 do not show a greater accuracy of prediction for any AEP flows when compared to the equations having multiple explanatory variables in the previous study. The calculated regression equations, basin characteristics, and at-site statistics will be incorporated into the U.S. Geological Survey web application, StreamStats ( https://streamstats.usgs.gov/ss/ ). This application allows users to select a location on a stream, whether gaged or ungaged, to obtain estimates of basin characteristics and flow statistics.

Puerto Rico↗

USGS2021

Forecasting drought probabilities for streams in the northeastern United States

Maximum likelihood logistic regression (MLLR) models for the northeastern United States forecast drought probability estimates for water flowing in rivers and streams using methods previously identified and developed. Streamflow data from winter months are used to estimate chances of hydrological drought during summer months. Daily streamflow data collected from 1,143 streamgages from April 1, 1877, through October 31, 2018, are used to provide hydrological drought streamflow probabilities for July, August, and September as functions of streamflows during October, November, December, January, and February. This allows estimates of outcomes from 5 to 11 months ahead of their occurrence. Models specific to the northeastern United States were investigated and updated. The MLLR models of drought stream-flow probabilities utilize the explanatory power of temporally linked water flows. Models with strong drought streamflow probability correct-classification rates were produced for streams throughout the northeastern United States. A test of northeastern United States drought streamflow probability predictions found that overall correct-classification rates for drought streamflow probabilities in the northeastern United States exceeded 97 percent when predicting July 2019 drought probability using February 2019 monthly mean streamflow data. Using hydrological drought probability estimates in a water-management context informs understandings of possible future streamflow drought conditions in the northeastern United States, provides warnings of potential future drought conditions, and aids water-management decision making and responses to changing circumstances.

Connecticut, Delaware, Massachusetts, Maine, New H↗

USGS2023

Status and trends of total nitrogen and total phosphorus concentrations, loads, and yields in streams of Mississippi, water years 2008–18

To assess the status and trends of conditions of surface waters throughout Mississippi, the U.S. Geological Survey, in cooperation with the Mississippi Department of Environmental Quality (MDEQ), summarized concentrations and estimated loads, yields, trends, and spatial and temporal patterns of total nitrogen (TN) and total phosphorus (TP) at 20 stream sites in MDEQ’s ambient water-quality monitoring network and 2 stream sites in the U.S. Geological Survey’s National Water-Quality Assessment Project’s monitoring network. Comparison of streamflow at the time of water-quality sample collection to flow-duration curves for each site showed that samples were relatively evenly spread over a wide range of flows, indicating that load estimations were representative of a wide range of flows. Relation of streamflow to concentrations of TN and TP varied among sites and land use. Sites with high agriculture land use in the drainage basin tended to have a positive correlation between streamflow and concentration, suggesting influence of event-driven nonpoint-source runoff. Sites near urban (developed) areas tended to have a negative correlation between streamflow and concentration, suggesting chronic point-source influences during low-flow conditions. Sites with high forest land use and lower agriculture and urban (developed) land use showed little to no association between streamflow and concentration. Seasonal distributions of concentrations of TN and TP also corresponded closely with variations in land use. Sites near urban (developed) land had the highest concentrations in late summer and fall, sites with a high percentage of agricultural land had the highest concentrations in the spring, and sites that were primarily forested or with little developed land did not exhibit substantial changes in concentration across seasons. Eight sites had statistical likelihoods for upward trends of TN loads, and seven sites had statistical likelihoods for downward trends. Trends in TN loads at six sites were considered “about as likely as not,” meaning that a site has an equal chance of having an upward or downward trend. Trend results of mean annual flow-normalized loads of TP for the period of analysis (2008–18) showed that 16 sites had upward trends, 3 sites had downward trends, and 2 sites were considered “about as likely as not.” Results from our study were compared to results from existing regional models to assess accuracy of predictions at a local scale. Comparisons of yields predicted from 2012 regional-scale SPAtially Referenced Regressions on Watershed attributes (SPARROW) to results from this study showed the 2012 SPARROW-predicted estimates varied in consistency with results from this study. The 2012 SPARROW-prediction model underestimated TN yields, more often and by a slightly larger degree, more than it overestimated TN yields. The 2012 SPARROW-predicted model tended to underestimate yields at study sites with higher yields. All four sites in the predominantly agricultural area of northwest Mississippi, locally known as the Mississippi Delta, were underestimated by 2012 SPARROW. For TP, yield comparisons at sites with lower yields were consistent, yields at sites with midrange yields tended to be overestimated by SPARROW, and yields at sites with high yields tended to be underestimated by SPARROW. TP yields at four sites in the Mississippi Delta were underestimated by the 2012 SPARROW-predicted model. Results of select sites from our study were also compared to other published load estimates from an earlier time period to evaluate possible trends. Comparison of TN yields at four sites and TP yields at three sites from the study-derived estimates to estimates made from data spanning 1993–2004 showed decreasing TN yields at all four sites and decreasing TP yields at two of three sites, with increasing yields of TP at the Yazoo River lower site. Also, a third comparison of the TN and TP yields of the Yazoo River lower site of this study to estimates made from data spanning 1996–97 showed decreasing TN yields but similar TP yields. This suggests that TN yields may have decreased over the last 20–30 years, but TP yields remain constant or are increasing.

Mississippi↗

USGS2026

Magnitude and frequency of peak and low flows in the Elkhorn River Basin, Nebraska, 1881–2022

Flood-frequency analysis is based on records of annual maximum instantaneous flows observed at long-term streamgages with 10 years or more of operation. Since the last flood-frequency analysis in Nebraska, an additional 30 years of annual peak-flow data have become available, and new flood-frequency analysis techniques have been developed. Moreover, the Elkhorn River Basin in north-central and eastern Nebraska has experienced two of the three highest magnitude floods on record in 2010 and 2019. The U.S. Geological Survey, in cooperation with the Nebraska Department of Transportation, analyzed flow frequency at streamgages in the Elkhorn River Basin in Nebraska. Flow data from the U.S. Geological Survey and the Nebraska Department of Water, Energy, and Environment annual hydrographic reports were utilized to analyze peak flows. The Peak flow FreQuency (PeakFQ) software was used to perform a flood-frequency and nonstationarity analysis on the selected streamgages in the Elkhorn River Basin in Nebraska. Results of the peak-flow nonstationarity analysis indicate that, of the 23 streamgages analyzed for peak-flow frequency, 4 showed trends that were likely increasing for annual peak flows, whereas 3 indicated trends that were somewhat likely to be increasing. For 11 streamgages, the trend was categorized as about as likely as not, meaning there is less than a 70-percent chance of the trend being either upward or downward. Additionally, 2 streamgages exhibited trends that were somewhat likely to be decreasing, and 3 streamgages showed trends that were likely decreasing. Low-flow streamflows and nonstationarity in the Elkhorn River Basin were analyzed for low flow periods representing the 1-day, 7-day, and 30-day flows at 21 streamgages using the Hydrologic Toolbox software. Spatially, the nonstationarity analysis results indicated likely increasing or somewhat increasing trend likelihoods for the 1-day, 7-day, and 30-day low flows for many of the Elkhorn streamgages downstream from the Elkhorn River at Ewing, Nebr., streamgage (U.S. Geological Survey station 06797500) and on eastern tributaries during the period of record.

Nebraska↗

USGS1954

Monazite in Atlantic shore-line features

This report is a survey of present and potential production of monazite from part of the Maryland-Florida section of the Atlantic Coastal Plain. The part of the Coastal Plain covered here is the outer (shore-ward) half. In this area, all the large heavy-mineral placers so far discovered occur in sand bodies that, by their shape, size, orientation, and lithology, appear to be ancient beaches, spits, bars, or dunes. Smaller placers have produced from recent shore-line features. The inner part of the Coastal Plain, to be treated in another report, is underlain generally by older rocks, ranging in age from Cretaceous to older Pleistocene. Only two large heavy-mineral placers are now in production at Trail Ridge, and near Jacksonville, both in Florida. Production is planned for the near future near Yulee, Fla.: in Folkston, Ga.: and at one or two localities in eastern North Carolina. Each of these three will produce monazite as a byproduct; the total new reserve for the three placers is about 33,000 tons of monazite. In large heavy-mineral placers of this type, monazite has not been found to run more than about 1 percent of total heavy minerals. In some large placers, notably Trail Ridge, it is almost or completely lacking. No reason for its sporadic occurrence has been found in this investigation. Two placers of potential economic value have been found by this project in Virginia, one west and one east of Chesapeake Bay. Neither is of promise for monazite production, but if they serve to open up exploration or production in the area, there is a chance for monazite as a byproduct from other placers. A discovery of considerable scientific interest has to do with the occurrence of two different suites of heavy minerals in the Coastal Plain, at least south of Virginia. One, an “older” suite, lacks epidote, hornblende, and garnet; this suite occurs in all older formations and in Pleistocene deposits lying above about 50 or 60 feet above sea level. The other, “younger” suite contains these three minerals: it is restricted to recent beaches and streams, and to Pleistocene deposits at low altitudes. Monazite may occur with either of these suites. The percentage of titania (TiO 2 ) in illmenite is of both scientific and economic interest. Illmenite is by far the most sought-for mineral in present exploration, and whether it contains the “normal” 53 percent of titania or, as it commonly does in Florida, 60 percent, is often of decisive importance in its exploitation. The nature, time, and place of this “enrichment” in titania has not been worked out. The heavy-mineral industry of the area seems to give promise of considerable expansion in the near future, and a greater monazite production seems assured.

Florida;Maryl;North Carolina;South Carolina;Virgin↗

USGS2015

Wildlife specimen collection, preservation, and shipment

Specimens are used to provide supporting information leading to the determination of the cause of disease or death in wildlife and for disease monitoring or surveillance. Commonly used specimens for wildlife disease investigations include intact carcasses, tissues from carcasses, euthanized or moribund animals, parasites, ingested food, feces, or environmental samples. Samples from live animals or the environment (e.g., contaminated feed) in the same vicinity as a mortality event also may be helpful. The type of specimen collected is determined by availability of samples and biological objectives. Multiple fresh, intact carcasses from affected species are the most useful in establishing a cause for a mortality event. Submission of entire carcasses allows observation of gross lesions and abnormalities, as well as disease testing of multiple tissues. Samples from live animals may be more appropriate when sick animals cannot be euthanized (e.g., threatened or endangered species) or for research and monitoring projects examining disease or agents circulating in apparently healthy animals or those not exhibiting clinical signs. Samples from live animals may include collections of blood, hair, feathers, feces, or ectoparasites, or samples obtained by swabbing lesions or orifices. Photographs and videos are useful additions for recording field and clinical signs and conveying conditions at the site. Collection of environmental samples (e.g., feces, water, feed, or soil) may be appropriate when animals cannot be captured for sampling or the disease agent may persist in the environment. If lethal collection is considered necessary, biologists should refer to the policies, procedures, and permit requirements of their institution/facility and the agency responsible for species management (U.S. Fish and Wildlife Service or State natural resource agency) prior to use in the field. If threatened or endangered species are found dead, or there is evidence of illegal take, field personal should contact local wildlife law enforcement authorities immediately and prior to handling the carcass. Prior to collecting samples, it is important to determine the capabilities and submission criteria of the laboratory receiving the samples. Some laboratories may specialize in a limited number of tests, be equipped to accept only certain types of tissues (instead of entire carcasses), or specialize in particular species or group of animals (e.g., reptiles, birds, mammals). Diagnostic laboratories have specific requirements regarding preparation, labeling, and shipping of samples. Adherence to these requirements helps ensure the usefulness of any submitted specimens. Although laboratories may vary in the cost and turnaround times for diagnostic tests, some laboratories may be able to prioritize samples and accommodate accelerated time frames if communicated at the time of submission. Keeping a prepacked kit with basic carcass-collection supplies, including a paper copy of the specimen history form (available for download from the Web sites of most diagnostic laboratories), in the office or vehicle will decrease the chances of forgetting an essential item and decrease response time for arriving at an event.

Techniques and Methods↗

USGS1975

Evaluation of reservoir sites in North Carolina: Regional relations for estimating the reservoir capacity needed for a dependable water supply

Draft-storage-frequency relations, which show the storage required for a reservoir to furnish a specified withdrawal or draft are regionalized for four zones in the State, using the mean annual flow of the streams as an index. The differences between the zones primarily reflect differences in the variability of stream flow. To assure the available draft will fall below 75 percent of the mean annual flow of a stream only once in 50 years on the average, a reservoir in the mountains would need a usable storage capacity of 45 percent of the mean annual runoff of the impounded stream. In comparison, reservoirs in parts of the Piedmont furnishing a draft of 75 percent of the mean annual flow must have usable storage equal to 60 percent of the mean annual runoff of the stream. In the inner Coastal Plain the storage required increases to 84 per-cent, and in the outer Coastal Plain to about 110 percent. These increases in storage necessary to furnish a certain draft are indicative of the general increase in streamflow variability, both seasonally and between years, that occurs from west to east in the State. Net evaporative draft, the evaporative loss from reservoirs when annual evaporation exceeds annual precipitation, also varies from west to east. For instance, a reservoir impounding a Piedmont stream, and designed with a 5 percent chance of deficiency, will have a net evaporative draft about twice as large as a similar sized reservoir in the Coastal Plain. In the mountains, annual precipitation always exceeds evaporation because of the cooler temperatures and higher rates of precipitation. Annual net evaporation is also proportionately smaller for large reser voirs than for small ones. On a Coastal Plain reservoir, with storage equivalent to the mean annual runoff of the stream and being drafted at 90 percent of the mean annual flow, the net evaporation for a stream with a mean annual runoff of only 500 acre-feet (0.62 cubic hectometres) is three times as great as for a stream with mean annual runoff of 100,000 acre-feet (123 cubic hectometres). Thus, one large reservoir has less evaporation loss than several small ones capable of furnishing, collectively, the same reliable draft. Under some circumstances, sedimentation can quickly reduce the available storage in a reservoir, thus decreasing the reliable draft. Estimated sedi-mentation rates in the Piedmont can range from 240 acre-feet per year (0.3 cubic hectometres per year) in a severely exposed drainage basin of 10 square miles (26 square kilometres) to 0.4 acre-feet per year (493 cubic metres per year) in a wooded basin of the same size. Seepage beneath and around a reservoir dam is normally not significant in the State. The usual engineering practices should be followed, however, to avoid locating the dam on an open or active fault, cavernous limestone, or continuous beds of sand or gravel.

North Carolina↗

USGS1978

Evaluation of thermograph data for California streams

Statistical analysis of water-temperature data from California streams indicates that, for most purposes, long-term operation of thermographs (automatic water-temperature recording instruments) does not provide a more useful record than either short-term operation of such instruments or periodic measurements. Harmonic analyses were made of thermograph records 5 to 14 years in length from 82 stations. More than 80 percent of the annual variation in water temperature is explained by the harmonic function for 77 of the 82 stations. Harmonic coefficients based on 8 years of thermograph record at 12 stations varied only slightly from coefficients computed using two equally split 4-year records. At five stations where both thermograph and periodic (10 to 23 measurements per year) data were collected concurrently, harmonic coefficients for periodic data were defined nearly as well as those for thermograph data. Results of this analysis indicate that, except where detailed surveillance of water temperatures is required or where there is a chance of temporal change, thermograph operations can be reduced substantially without affecting the usefulness of temperature records.

California↗

USGS1980

Water resources of the Port Gamble Indian Reservation, Washington

This report provides information on the water resources of the Port Gamble Indian Reservation, Washington, including ground- and surface-water quality and quantity data and interpretations of the data. This information was gathered to provide a base for management and protection of the water resources of the reservation. Ground water in the study area generally occurs in two aquifers. A shallow aquifer in weathered till (or fine sand and gravel) generally yields only enough water to wells to supply one or two households, and a lower artesian-aquifer system of sand and gravel layers near or below sea level produces higher yields--more than 65 gallons per minute to at least one well. Future supplies of ground water probably can be withdrawn from the lower artesian-aquifer system almost anywhere beneath the reservation. The estimated natural discharge of ground water from the lower artesian-aquifer system to Hood Canal and Port Gamble (bay) is about 42,000 cubic feet per day, or an average of about 220 gallons per minute. Of this amount, it is estimated that about 90 gallons per minute can be economically withdrawn, probably without greatly increasing chances of seawater intrusion. One well in the area taps a still deeper artesian aquifer that is otherwise unexplored. This aquifer, 75 to 80 feet or more below sea level, could possibly supply additional ground water for future use. Ground-water quality is good, but the water is moderately hard and has moderately high iron concentrations. Chloride analyses indicate that in 1977 there was no seawater intrusion into the lower aquifer tapped by wells in the community of Little Boston.

Washington↗

USGS1981

Water type and suitability of Oklahoma surface waters for public supply and irrigation; Part 2: Salt Fork Arkansas and Cimarron River basins through 1978

Water-quality data in the Salt Fork Arkansas and Cimarron River basins within Oklahoma, through 1978, were examined for water type and suitability for public water supply and irrigation use. Of 76 stations with available data, 32 stations or 42 percent were considered to have sufficient data for analysis. The classification of water type was based on the relation of the major ions: calcium, magnesium, sodium, carbonate, bicarbonate, sulfate, and chloride to each other within the range of measured specific conductance. The suitability for use as a public supply was based on the concentration distribution of selected constituents. The constituents selected were those with maximum contaminant levels established by regulation, or constituents for which recommended maximum limits have been established and for which historic data are available. The irrigation classification method of Wilcox was used to relate sodium, calcium, and magnesium concentrations and the salinity distribution to the use of the water for irrigation. Where data were available, the chance of phytotoxic effects by boron was discussed.

Oklahoma↗

USGS1981

Water type and suitability of Oklahoma surface waters for public supply and irrigation, Part 3: Canadian, North Canadian, and deep fork river basins through 1979

Water-quality data through 1979 in the Canadian, North Canadian, and Deep Fork River basins within Oklahoma were examined for water type and suitability for public water supply and irrigation use. Of 105 stations with available data, 47 stations or 45 percent were considered to have sufficient data for analysis. The classification of water type was based on the relation of the major ions: calcium, magnesium, sodium, carbonate, bicarbonate, sulfate, and chloride to each other within the range of measured specific conductance. The suitability for use as a public supply was based on the concentration distribution of selected constituents. The constituents selected were those with maximum contaminant levels established by regulation, or constituents for which recommended maximum limits have been established and for which historic data are available. The irrigation classification method of Wilcox was used to relate sodium, calcium, and magnesium concentrations and the salinity distribution to the use of the water for irrigation. Where data were available, the chance of phytotoxic effects by boron was discussed.

Oklahoma↗

USGS1982

Water type and suitability of Oklahoma surface waters for public supply and irrigation, Part 5: Washita river basin through 1979

Water-quality data through 1979 in the Washita River basin within Oklahoma were examined for water type and suitability for public water supply and for irrigation use. Of 82 stations with available data, 32 stations or 39 percent were considered to have sufficient data for analysis. The classification of water type was based on the relation of the major ions: calcium, magnesium, sodium, carbonate, bicarbonate, sulfate, and chloride to each other within the range of measured specific conductance. The suitability for use as a public supply was based on the concentration distribution of selected constituents. The constitu ents selected were those with maximum contaminant levels established by regulation, or constituents for which recommended maximum limits have been established and for which historic data are available. The irriga tion classification method of Wilcox was used to relate sodium, calcium, and magnesium concentrations and the salinity distribution to the suita bility for use of the water for irrigation. Where data were available, the chance of phytotoxic effects by boron was discussed.

Oklahoma↗

USGS1981

Water type and suitability of Oklahoma surface waters for public supply and irrigation Part 4: Red River mainstem and North Fork Red River basin through 1979

Water-quality data for the Red River mainstem and the North Fork Red River basin within Oklahoma, through 1979, were examined for water type and suitability for public water supply and irrigation use. Of 96 stations with available data, 53 stations or 55 percent were considered to have sufficient data for analysis. The classification of water type was based on the relation of the major ions: calcium, magnesium, sodium, carbonate, bicarbonate, sulfate, and chloride to each other within the range of measured specific conductance. The suitability of the water for use as a public supply was based on the concentration distribution of selected constituents. The constituents selected were those with maximum contaminant levels established by regulation, or constituents for which recommended maximum limits have been established and for which historic data are available. The irrigation-classification method of Wilcox was used to relate sodium, calcium, and magnesium concentrations and the salinity distribution to the use of the water for irrigation. If data are available, the chance of phytotoxic effects by boron is discussed.

Oklahoma↗

USGS1983

Debris flow hazard assessment for the Oregon Caves National Monument

After experiencing a devastating debris flow in the Oregon Caves National Monument, the National Park Service needs an evaluation of the hazard of additional flows. Soil properties at six random sites were compared with those at the source of the debris flow. Although all sites had soils that could become unstable with sufficient moisture, soil at one site had properties similar to those at the scar and the potential for another flow was confirmed. The report suggests that winter weather conditions be closely monitored and compared to the antecedent conditions prior to the known failure. When the threshold for additional mass wasting is believed imminent, appropriate action can be taken to insure the safety of work personnel and the public. The peak streamflow that preceded the 5,200 cu yds of debris is estimated to have a 0.5 percent chance of being equaled or exceeded in any given year. (USGS)

Water-Resources Investigations Report↗

USGS1986

Methods for estimating magnitude and frequency of floods in Montana based on data through 1983

Equations are presented for estimating flood magnitudes for ungaged sites in Montana based on data through 1983. The State was divided into eight regions based on hydrologic conditions, and separate multiple-regression equations were developed for each region. These equations relate annual flood magnitudes and frequencies to basin characteristics and are applicable only to natural-flow streams. In three of the regions, equations also were developed relating flood magnitudes and frequencies to basin characteristics and channel-geometry measurements. The standard errors of estimate for an exceedance probability of 1 percent ranged from 39 to 87 percent. Techniques are described for estimating annual flood-magnitude and flood-frequency information at ungaged sites based on data from gaged sites on the same stream. Included are curves relating flood-frequency information to drainage area for eight major streams in the State. Maximum known flood magnitudes in Montana are compared with estimated 1-percent-chance flood magnitudes and with maximum known floods in the United States. Values of flood magnitudes for selected exceedance probabilities and values of significant basin characteristics and channel-geometry measurements for all gaging stations used in the analysis are tabulated. Included are 375 stations in Montana and 28 nearby stations in Canada and adjoining States.

Montana↗

USGS1990

Flood frequency of the Savannah River at Augusta, Georgia

To fill an increasing need for reliable information on floods of various recurrence intervals on the Savannah River a flood-frequency relation was developed for the long-term gaging station at Augusta, Georgia. The flood-frequency analysis was complicated by the fact that the Savannah River upstream of Augusta has experienced increasing regulation of flow caused by three large dams constructed since 1952. The pre-impoundment period was important to the flood-frequency analysis because it included a number of large floods that, even when adjusted for regulation, exceed all floods since 1952. A reservoir routing model was used to adjust nine such floods for the effects of regulation, and to develop a relation for estimating regulated peak discharges for additional unregulated floods. The 1% chance exceedance flood for regulated conditions on the Savannah River at Augusta was computed as 180,000 cu ft/sec. (USGS)

Georgia↗